Claire Goursaud

On the benefits of random FDMA schemes in ultra narrow band networks

Ultra narrow band transmission (UNB) systems have already been deployed and have proved to be ultra-efficient for point-to-point communications. This paper presents this technology and gives some insights on the scalability of UNB for a multi-point to point network. This configuration corresponds to an uplink scenario where multiple nodes compete to send their packets, with neither coordination nor feedback from the sink. In particular, we present and analyze two multiple access schemes based on random frequency selection: discrete random FDMA (DR-FDMA) and the new continuous random FDMA (CR-FDMA). An ideal system where the carrier frequencies are exactly obtained is first considered and extended to a more realistic case, with rough carrier frequencies. We analyze the system performance in terms of bit error rate and outage probability. The presented results clearly show that, even if in the ideal case, the DR-FDMA scheme outperforms the CR-FDMA scheme; in the realistic case, both schemes lead to similar performance. Thus, this paper highlights the fact that the use of CR-FDMA is very relevant in a realistic network as it bypasses the need of an accurate carrier frequency control, and thus permits the use of even the cheapest transmitters without loss of performance.

Qualitative analysis of RSSI behavior in cooperative wireless body area networks for mobility detection and navigation applications

In this paper, we account for radio-location experiments aiming at both indoor navigation and mobility detection applications for Wireless Body Area Networks (WBAN). This measurement campaign involved IEEE 802.15.4-compliant integrated radio devices organized within a full mesh topology over on-body and off-body links. The latter devices produce peer-to-peer Received Signal Strength Indicators (RSSI) that could feed ranging, positioning or tracking algorithms. An in-depth behavioral analysis of the collected time-stamped radio-location metrics is thus proposed with respect to the captured human mobility (including body shadowing). Based on our observations and interpretations, practical insights are finally drawn in terms of system and algorithms design.

Random unslotted time-frequency ALOHA: Theory and application to IoT UNB networks

The ALOHA protocol is regaining interest in the context of the Internet of Things (IoT), especially for Ultra Narrow Band (UNB) signals. In this case, the classical assumption of channelization is not verified anymore, modifying the ALOHA performances. Indeed, UNB signals suffer from a lack of precision on the actual transmission carrier frequency, leading to a behavior similar to a frequency unslotted random access. In this paper, the success probability and throughput of ALOHA is generalized to further describe frequency-unslotted systems such as UNB. The main contribution of this paper is the derivation of a generalized expression of the throughput for the random time-frequency ALOHA systems. Besides, this study permits to highlight the duality of ALOHA in time and frequency domain.

Optimization of the predefined number of replications in a Ultra Narrow Band based IoT network

Ultra Narrow Band networks using Random-FTMA scheme are mainly characterized by the randomness both in time and frequency domain. The frequency randomness prevents from allocating orthogonal resources for transmission, and induces uncontrolled interference. By introducing diversity, replication mechanism is a promising candidate to enhance the reliability of such wireless network. Therefore, in this paper, by taking into account the randomness both in time and frequency domain, the replication mechanism has been considered. Considering the outage probability, we theoretically evaluate the system performance and show that there exists an optimal number of transmissions. Finally, we highlight that this number of repetitions can be easily optimized by considering a unique global parameter.

Theoretical analysis of UNB-based IoT networks with path loss and random spectrum access

UNB is dedicated to long range and low power transmission in IoT networks. The channel access is Random-FTMA, where nodes select their time and frequency in a random and continuous way. This randomness leads to a new behavior of the interference which has not been theoretically analyzed yet, when considering the pathloss of nodes located randomly in an area. In this paper, in order to quantify the system performance, we derive and exploit a theoretical expression of the packet error rate in a UNB based IoT network, when taking into account both interference due to the spectral randomness and path loss due to the propagation.

Enhancement optimized MAC protocol for medical applications

Growth of elderly population induces the increasing demands for high-quality healthcare services, wireless body area networks (WBANs) has emerged as a promising solution for monitoring of patients vital life signs parameters. Reliability and extending the lifetime are considered amongst the important and challenging issues in WBANs. The standard IEEE 802.15.4 is considered as the most used MAC protocol for medical sensor body area networks, owing to its low-power, low data rate and low-cost features. In this paper, we propose an enhancement optimized MAC protocol based on IEEE 802.15.4 dubbed EOMAC. The proposed protocol aims to enhance the reliability and to prolong the lifetime of the network, by reducing energy consumption.

On the benefits of successive interference cancellation for ultra narrow band networks : Theory and application to IoT

UNB (Ultra Narrow Band) stands out as one promising PHY solution for low-power, low-throughput and long-range IoT. The dedicated MAC scheme is RFTMA (Random Frequency and Time Multiple Access), where nodes access the channel randomly both in frequency and in time domain, without prior channel sensing. This blind randomness sometimes introduces interference and packet losses. Hence, in this paper, we propose to use the well-known SIC (Successive Interference Cancellation) to cancel the interference in a recursive way. We provide a theoretical analysis of network performance, when considering jointly SIC and the specific spectral randomness of UNB. We analytically and numerically highlight the SIC efficiency in enhancing UNB system performance.